Professor Layton games tend to take their time getting to the states, but his first 3DS outing could be coming next year. At the very least, Level-5 is teasing the 3DS game Mask of Miracle in Europe for next year, and Layton games tend to hit North America before the territory, so that gives us a hopeful sign.
The tease of "an all-new Layton next year" came at the end of a trailer for Professor Layton and the Last Specter (or Spectre's Call in the region). It was spotted by N-Europe (via Joystiq). Mask of Miracle is one of two announced Layton 3DS games, but the other, Professor Layton vs Ace Attorney, isn't even due in Japan until next year. Shacknews has contacted Nintendo of America regarding a domestic release.
Layton games are heavy on text, between the dialogue-heavy story and making sure all of the puzzles are clear, so localization tends to take a while. Mask of Miracle was released in February in Japan, so we'll wait at least a year for it -- but that's better than the nearly two years it took to bring us Last Specter. Progress!